Continuing investigations will determine more completely the transport, metabolism and function of flavins, especially as involve systems essential to mammals including humans. Specific aims and the nature of informatin sought include: 1. Riboflavin-binding proteins - comparative properties from different animal tissues, developmental aspects, probable means for release and function as carriers, hormonal control, and detailed molecular characteristics. 2. Flavokinase - molecular properties including nature of the active site, nature of substrate induction, hormonal regulation, and potential interactions between riboflavin-binding proteins that supply substrate and FAD synthetase which subsequently acts upon the product. 3. FAD synthesase - complete purification, determine general molecular properties, more throughly circumscribe substrate specificty, detail the nature of the active site, and assess regulatory control and interactions. 4. Biosyntheses and metabolism of "covalent" flavings - relative rates of formationa nd turnover in vivo of the particulately included flavoprotein, viz. the four of mitochondrial localization (e.g. succinate dehydrogenase and monoamine oxidase), and the microsomal L-gulonolactone oxidase, and subsequent enzymatic steps in the catabolic degradation of the amino acid-flavin subportions. 5. Pyridoxamine(pyridoxine)5'-phosphate oxidase - detail kinetics on binding and release of flavoenzyme, substrates, product and inhibitors, ascertain stereospecificity for hydrogen abstraction, sequence the two polypeptide chains of the catalytically active monomer, ascertain in vivo dependency on rate-limiting supply of FMN as well as quantitate level of activity as relates to riboflavin status.